Work carried out during the past year has shown that: 1) Axon sprouting in the deafferented hippocampus begins 5 to 6 days after lesion and continues vigorously for several days thereafter; 2) The sprouting response is preceded by a period of intense astroglial and microglial activity; 3) The afferents of the hippocampus reach that structure at about 5 days post-natal and develop a laminated organization shortly thereafter. Experiments to be conducted during the coming year include: 1) Analysis of the time course of sprouting in neonatal rats; 2) The effects of blocking glial cell mitosis on glial and neuronal responses to deafferentation; 3) Extension of pilot studies on the presence of diffusable mitoitic "factors" in the deafferented hippocampus.